As conventional materials for automobiles, particularly insulated electric wires to be cabled in the interior, there have been frequently used those wherein a conductor such as a copper wire is coated with a resin composition based on polyvinyl chloride resin (hereinafter, referred to as “PCV resin composition” herein). The polyvinyl chloride resin has excellent material properties that flame retardancy is high since it is a self-extinguishing material, hardness can be freely controlled by adding a plasticizer, and abrasion resistance is high. However, the resin may generate harmful gasses such as halogen-based gases in incineration or burning at vehicle fire, which cause environmental problems.
Thus, in recent years, halogen-free resin compositions based on polyolefin-based resins have been developed. In such halogen-free resin compositions, long-term stability of mechanical strength is improved through prevention of decomposition and deterioration by adding various stabilizers such as an oxidation stabilizer and a light stabilizer to the polyolefin-based resins (e.g., see Patent Document 1).
Moreover, by adding an inorganic flame retardant such as a metal hydrate as a flame retardant, flame retardancy can be improved with maintaining the halogen-free property. However, the metal hydrate should be added in a large amount, but the addition invites decrease in properties of the polyolefin-based resins, e.g., a remarkable decline in mechanical properties and flexibility.
[Patent Document 1] JP-A-2006-83328